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UK DVB-T radio timing problems since 0.25

 

 

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John.Veness.mythtv at pelago

May 2, 2012, 7:12 AM

Post #1 of 6 (512 views)
Permalink
UK DVB-T radio timing problems since 0.25

Hi,

I've just updated to MythTV 0.25 (previously 0.24) using the Mythbuntu
packages, on Ubuntu 11.10. I didn't change the underlying Ubuntu version
at the same time.

Since 0.25, playing back programs on UK DVB-T (Freeview) radio channels
shows screwy timecode problems. For example, a 35 minute recording plays
as a 29 min 11 seconds recording. That is, the total length shows as 35
minutes, but the current position marker will change from zero to
29min11 before stopping. During that time it will play the entire 35
minute recording at normal speed. In other words, the current position
marker is lagging behind real time.

Also, when skipping forward or backward, e.g. by 30 seconds or by 10
minutes, there is a noticeable delay of a second or so before the skip
takes place and before the OSD pops up. Doing lots of skipping feels a
bit like wading through treacle, like it is having problems finding the
position in the file to seek to.

Both of these things were fine on identical hardware and identical
underlying Ubuntu version with MythTV 0.24. Note that these problems
occur both with new recordings made with 0.25 and old recordings made in
0.24.

Before I report this as a bug, I wondered if anyone else had seen these
problems or knew of a fix?

Cheers,

John

--
John Veness, MythTV user, UK, DVB-T
_______________________________________________
mythtv-users mailing list
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mythtv at duncb

May 3, 2012, 1:30 AM

Post #2 of 6 (483 views)
Permalink
Re: UK DVB-T radio timing problems since 0.25 [In reply to]

On 02/05/2012 15:12, John Veness wrote:
> Hi,
>
> I've just updated to MythTV 0.25 (previously 0.24) using the Mythbuntu
> packages, on Ubuntu 11.10. I didn't change the underlying Ubuntu
> version at the same time.
>
> Since 0.25, playing back programs on UK DVB-T (Freeview) radio
> channels shows screwy timecode problems. For example, a 35 minute
> recording plays as a 29 min 11 seconds recording. That is, the total
> length shows as 35 minutes, but the current position marker will
> change from zero to 29min11 before stopping. During that time it will
> play the entire 35 minute recording at normal speed. In other words,
> the current position marker is lagging behind real time.
>
> Also, when skipping forward or backward, e.g. by 30 seconds or by 10
> minutes, there is a noticeable delay of a second or so before the skip
> takes place and before the OSD pops up. Doing lots of skipping feels a
> bit like wading through treacle, like it is having problems finding
> the position in the file to seek to.
>
> Both of these things were fine on identical hardware and identical
> underlying Ubuntu version with MythTV 0.24. Note that these problems
> occur both with new recordings made with 0.25 and old recordings made
> in 0.24.
>
> Before I report this as a bug, I wondered if anyone else had seen
> these problems or knew of a fix?
>
> Cheers,
>
> John
>
Seeing this here too

Dunc
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John.Veness.mythtv at pelago

May 3, 2012, 2:58 AM

Post #3 of 6 (484 views)
Permalink
Re: UK DVB-T radio timing problems since 0.25 [In reply to]

On 02/05/2012 15:12, John Veness wrote:
> Hi,
>
> I've just updated to MythTV 0.25 (previously 0.24) using the Mythbuntu
> packages, on Ubuntu 11.10. I didn't change the underlying Ubuntu version
> at the same time.
>
> Since 0.25, playing back programs on UK DVB-T (Freeview) radio channels
> shows screwy timecode problems. For example, a 35 minute recording plays
> as a 29 min 11 seconds recording. That is, the total length shows as 35
> minutes, but the current position marker will change from zero to
> 29min11 before stopping. During that time it will play the entire 35
> minute recording at normal speed. In other words, the current position
> marker is lagging behind real time.
>
> Also, when skipping forward or backward, e.g. by 30 seconds or by 10
> minutes, there is a noticeable delay of a second or so before the skip
> takes place and before the OSD pops up. Doing lots of skipping feels a
> bit like wading through treacle, like it is having problems finding the
> position in the file to seek to.
>
> Both of these things were fine on identical hardware and identical
> underlying Ubuntu version with MythTV 0.24. Note that these problems
> occur both with new recordings made with 0.25 and old recordings made in
> 0.24.
>
> Before I report this as a bug, I wondered if anyone else had seen these
> problems or knew of a fix?

Since I wrote the above, I've realised I haven't described the problem
correctly. The second paragraph should be:

Since 0.25, playing back programs on UK DVB-T (Freeview) radio channels
shows screwy timecode problems. For example, a 35 minute recording plays
as a 29 min 10 seconds recording. That is, the total length shows as 35
minutes, but the current position marker will change from zero to
29min10 before stopping. The last almost 5 minutes 50 seconds of the
recording will not play in Myth.

Note that if I watch the filesystem as the program is recording, I do
see the filesize increasing during the last six minutes of the
recording. Also, if I play back the file with something else, e.g.
ffplay, it will play the full 35 minutes. So this is a problem with
playback in Myth, not with recording.

I notice with interest that 35 minutes is 2100 seconds, and 29 minutes
10 seconds is 1750 seconds. 2100/1750 is 1.2, or the same as 60/50. Is
this some kind of 60fps vs 50fps mismatch?

These recordings have no video, just audio and MHEG. Maybe because they
have no video, Myth is making a guess at 60 frames per second rather
than (as it should be in UK) 50 frames per second. It then does some
kind of calculation and plays what it thinks is the correct length but
stops early. I haven't checked the code, so this is just a guess. Note
that as far as I can tell, the recording is playing back at correct
speed and pitch.

Does anyone want a sample file?

Cheers,

John

--
John Veness, MythTV user, UK, DVB-T
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://www.mythtv.org/mailman/listinfo/mythtv-users


rick at timeforabrew

May 11, 2012, 1:33 PM

Post #4 of 6 (432 views)
Permalink
Re: UK DVB-T radio timing problems since 0.25 [In reply to]

On May 3, 2012 10:58 AM, "John Veness" <John.Veness.mythtv [at] pelago>
wrote:
>
> On 02/05/2012 15:12, John Veness wrote:
>>
>> Hi,
>>
>> I've just updated to MythTV 0.25 (previously 0.24) using the Mythbuntu
>> packages, on Ubuntu 11.10. I didn't change the underlying Ubuntu version
>> at the same time.
>>
>> Since 0.25, playing back programs on UK DVB-T (Freeview) radio channels
>> shows screwy timecode problems. For example, a 35 minute recording plays
>> as a 29 min 11 seconds recording. That is, the total length shows as 35
>> minutes, but the current position marker will change from zero to
>> 29min11 before stopping. During that time it will play the entire 35
>> minute recording at normal speed. In other words, the current position
>> marker is lagging behind real time.
>>
>> Also, when skipping forward or backward, e.g. by 30 seconds or by 10
>> minutes, there is a noticeable delay of a second or so before the skip
>> takes place and before the OSD pops up. Doing lots of skipping feels a
>> bit like wading through treacle, like it is having problems finding the
>> position in the file to seek to.
>>
>> Both of these things were fine on identical hardware and identical
>> underlying Ubuntu version with MythTV 0.24. Note that these problems
>> occur both with new recordings made with 0.25 and old recordings made in
>> 0.24.
>>
>> Before I report this as a bug, I wondered if anyone else had seen these
>> problems or knew of a fix?
>
>
> Since I wrote the above, I've realised I haven't described the problem
correctly. The second paragraph should be:
>
> Since 0.25, playing back programs on UK DVB-T (Freeview) radio channels
shows screwy timecode problems. For example, a 35 minute recording plays as
a 29 min 10 seconds recording. That is, the total length shows as 35
minutes, but the current position marker will change from zero to 29min10
before stopping. The last almost 5 minutes 50 seconds of the recording will
not play in Myth.
>
> Note that if I watch the filesystem as the program is recording, I do see
the filesize increasing during the last six minutes of the recording. Also,
if I play back the file with something else, e.g. ffplay, it will play the
full 35 minutes. So this is a problem with playback in Myth, not with
recording.
>
> I notice with interest that 35 minutes is 2100 seconds, and 29 minutes 10
seconds is 1750 seconds. 2100/1750 is 1.2, or the same as 60/50. Is this
some kind of 60fps vs 50fps mismatch?
>
> These recordings have no video, just audio and MHEG. Maybe because they
have no video, Myth is making a guess at 60 frames per second rather than
(as it should be in UK) 50 frames per second. It then does some kind of
calculation and plays what it thinks is the correct length but stops early.
I haven't checked the code, so this is just a guess. Note that as far as I
can tell, the recording is playing back at correct speed and pitch.
>
> Does anyone want a sample file?
>
>
> Cheers,
>
> John
>
> --
> John Veness, MythTV user, UK, DVB-T
> _______________________________________________
> mythtv-users mailing list
> mythtv-users [at] mythtv
> http://www.mythtv.org/mailman/listinfo/mythtv-users

I'm also seeing this. Usually my radio recordings are just extracted to mp3
rather than listened to directly on a mythfrontend so I hadn't noticed it.

I've played back a couple of recordings via the frontend and see the same
thing. One recording is 38.00 minutes and the internal player stops at
31.38. Another recording of 19.00 exits at 15.53. MHEG being disabled makes
no difference.

If its relevant, I took a look at the 'playback data' available via the
playback menu and compared a radio broadcast to a normal one. The normal
one displays FPS: 25.060.01, video: 720x576 [at] 25, while the radio
broadcast displays FPS:30.030.01, video: 0x0 [at] 29

Cheers,
Rick


John.Veness.mythtv at pelago

May 14, 2012, 2:36 AM

Post #5 of 6 (415 views)
Permalink
Re: UK DVB-T radio timing problems since 0.25 [In reply to]

On 11/05/2012 21:33, Rick Lane wrote:
> I'm also seeing this. Usually my radio recordings are just extracted to
> mp3 rather than listened to directly on a mythfrontend so I hadn't
> noticed it.
>
> I've played back a couple of recordings via the frontend and see the
> same thing. One recording is 38.00 minutes and the internal player stops
> at 31.38. Another recording of 19.00 exits at 15.53. MHEG being disabled
> makes no difference.
>
> If its relevant, I took a look at the 'playback data' available via the
> playback menu and compared a radio broadcast to a normal one. The normal
> one displays FPS: 25.060.01, video: 720x576 [at] 25, while the radio
> broadcast displays FPS:30.030.01, video: 0x0 [at] 29
>
> Cheers,
> Rick

Hi Rick,

Thanks for confirming. I notice that 31.38 is 25/30ths of 38.00, and
15.53 is 25/30ths of 19.00.

I've found that I've actually described the problem incorrectly twice
now, earlier in this thread (it turns out due to confusions with
skipping and edit points)!

I don't know if you're seeing the same thing, but for me, if I play back
one of these recordings and don't press any buttons, everything plays
back fine. It's only if I skip that things go wrong. For example, if I
skip forward 10 minutes, the OSD will say that I'm 10 minutes into the
recording, but actually it's more like 12. If I skip forward another 10
minutes, the OSD will say that I'm 20 minutes into the recording, but
actually it's more like 24. I think there also might be a problem with
edit points, but I haven't investigated fully yet.

I intend to file a bug and host a recording file somewhere for devs to
analyse, but haven't got around to it yet. If a dev is reading this and
has worked out what's going on, that would be great.

Cheers,

John

--
John Veness, MythTV user, UK, DVB-T
_______________________________________________
mythtv-users mailing list
mythtv-users [at] mythtv
http://www.mythtv.org/mailman/listinfo/mythtv-users


J.Pilk at tesco

May 14, 2012, 3:46 AM

Post #6 of 6 (406 views)
Permalink
Re: UK DVB-T radio timing problems since 0.25 [In reply to]

On 14/05/12 10:36, John Veness wrote:
> On 11/05/2012 21:33, Rick Lane wrote:
>> I'm also seeing this. Usually my radio recordings are just extracted to
>> mp3 rather than listened to directly on a mythfrontend so I hadn't
>> noticed it.
>>
>> I've played back a couple of recordings via the frontend and see the
>> same thing. One recording is 38.00 minutes and the internal player stops
>> at 31.38. Another recording of 19.00 exits at 15.53. MHEG being disabled
>> makes no difference.
>>
>> If its relevant, I took a look at the 'playback data' available via the
>> playback menu and compared a radio broadcast to a normal one. The normal
>> one displays FPS: 25.060.01, video: 720x576 [at] 25, while the radio
>> broadcast displays FPS:30.030.01, video: 0x0 [at] 29
>>
>> Cheers,
>> Rick
>
> Hi Rick,
>
> Thanks for confirming. I notice that 31.38 is 25/30ths of 38.00, and
> 15.53 is 25/30ths of 19.00.
>
> I've found that I've actually described the problem incorrectly twice
> now, earlier in this thread (it turns out due to confusions with
> skipping and edit points)!
>
> I don't know if you're seeing the same thing, but for me, if I play back
> one of these recordings and don't press any buttons, everything plays
> back fine. It's only if I skip that things go wrong. For example, if I
> skip forward 10 minutes, the OSD will say that I'm 10 minutes into the
> recording, but actually it's more like 12. If I skip forward another 10
> minutes, the OSD will say that I'm 20 minutes into the recording, but
> actually it's more like 24. I think there also might be a problem with
> edit points, but I haven't investigated fully yet.
>
> I intend to file a bug and host a recording file somewhere for devs to
> analyse, but haven't got around to it yet. If a dev is reading this and
> has worked out what's going on, that would be great.
>
> Cheers,
>
> John
>
I see something else that might be related to this when trying to edit
HD dvb-t2 recordings. If I try to resume play from a point a few
minutes from the end it just exits. If I have a cut defined earlier it
will resume as expected and play to the end. I haven't really tried to
define the exact circumstances yet. And I opened a ticket some time ago
about previewgen assuming a 30fps framerate. That got won'tfixed. It's
unimportant but perhaps related, too.

John P


John P

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